Most of us won’t have metallic sodium in a little bottle of kerosene, but all the refraction methods will work in the sunshine.

When I was in high school, fire investigators figured out that whoever started a string of forest fires had positioned the thick glass bottoms of gallon jugs to focus the sun on grass and leaves. It didn’t need to be set when the grass was dry, because conditions would dry out soon enough. Can’t remember whether they ever caught him/her.